Electropneumatic loud-speaker



Oct. 18, 1949.

J. l.. FoDoR ELECTROPNEUMATIC LOUD-SPEAKER 2 Sheets-Sheet 1 Filed Jan. 29, 1946 Oct. 1s, 1949. J, FODOR 2,485,269

ELECTROPNEUMATIC LOUD-'SPEAKER Filed Jan. 29, 1946 2 Sheets-Sheet 2 zy/l?. 6.

INVENTOR sfpf/ Foooe.

ATTORNEY Patented Oct. 18, 1949 UN I T ED S TAT ES T OFFICE 2,485,269 ELEcTROPNEUMATICnoun:`sriu1i1nza Joseph L. Fodor, South Norwalk, -xGomL Application January 29, 1946'Se1ialfNm 644,148

13'Claims. 1

This invention relates to sound Yreproducing and amplifying means. It is applicable, forexample, to the construction of loud speakers.

An object of the invention is to provide such a device, in ywhich an air stream is modulated Vto generate sounds, with means for mounting the modulating means s0 that it will be extremely Avsensitive to vibratory impulses transmitted toit.

1 Another object of the invention is to provide air valve means of improved eil'iciency, comprising a plurality of slotted diaphragms separately open to the passage of air but adapted when superimposed to form an air seal in which the valve members, when the device is in use, will be spaced apart more uniformlyand more nearly 'in parallel relation than in prior art devices thereby rendering all the slots of said diaphragms open for the passageof air and thus facilitating a maximum rflow of air through the device.

Another object of the invention is toprovide lan improved assembly in'which the closing movement of a delicately balanced movablediaphragm lis Iprogressively cushioned and undesired vibration due to striking together of the diaphragm members is minimized.

Another object of the invention is to provide such diaphragm mounting means With means facilitating adjustment of the relative positions of movable and xed slotted valve members.

Another object of the invention is .to ,provide simple, practical and ecient apparatus of the above mentioned kind.

Other objects-of .the invention will Cbe .in -part obvious or in part pointed out hereinafter.

The invention accordingly consists :in the tfeatures of construction, combinations of elements, arrangements of parts, and in the several steps and relation and order of each of said -steps =to one or more of the others thereof, `all1as will lbe pointed out in the following description, andthe scope of the application of which will be indicated inthe following claims.

The invention will lbest be understood `if 'the following description 'is read in connection fwith the drawings, in which,

Figure 1 is a vertical section through a device embodying my invention;

Figure la is a detail View showing the outer ends of the air outlet and inlet passages;

Figure 2 is a plan view ofthe device withltl'ie cover removed;

VFigure 3 is a transverse sectional View "taken through-the voice-coil and -magnet assembly on thef1ine-'3-3 of Figure '11;

Figure 4 yis 'a 'detail perspective view '.of Vthe valve means employed; :and

:Figure ,5 is 'a perspective Vviewshowing the assembled `voice coil :and pole :pieces as a unit `ready fior insertion lin ,the device;

Figure 6 is 'a plan 'View 'of the device, similar to lFigure l'2, S'but `with 'the cover plate entirely removed; -and Figure?? `is a :cross sectional view taken-on the'line l-l of Figure 6.

In the embodiment of the 'invention Yas illustrated hereinal-hollowchamberis provided comprising the base member l0 and the cover `|2 secured together "as J'byfscrews l'4 `which extend vthrough bores i6 'provided 'at *intervals around the marginal flange 1'8 'o'f base Amember l0 and engage internally 'threaded -bores `providedin lugs 2D extending upwardly faround 'the marginal ange 2-2 `oi casing'cover |`2.

Within the closure JAformed by 'the members I0 and l2 means xare provided for vibrating a diaphragm or grid to generate 'sound impulses Within thesaidchamber. 'The source of -vibratory fenergy, vas illustrated lherein, comprises a voice fcoilfa'nd magnet assembly, the 'Voice coil being connected in 'a #circuit through which may be supplied `electrical impuls'e's, which, -for example, may have been translated vinto electrical energy ffromsound impulses l'delivered at a distance, 'as Afor example through a microphone 'connected' in said circuit.

Preferably =said assembly vcomprises Ya permanent `magnet 24 -to amplify fthevibratory 'im- =pulsesfdelivered toanarmature 2'6'which extends iinto the center o'f fa -voice v'coil 28, `which lmay Y 'be Wound on Va vspool-'like lsupport `30 `having an aperture 732 1'extending -jaxially through the hub xof vthe yspool @and positioned between Ithe pole l pieces T321 and 36. `illustrated vthe spool-'like support :30 Vfcomprises two complementary parts having=the-interttingfopenhub portions v30a and '30h (Figure '3) The lvoice coil assembly is. shown'ilxe'd in position betweenfthe'parallel-arms of magnet 2'4 by iscrews '33 I, which 'extendthrough va plate J33 overlying the assembly and-are threadedly engaged in the "upper surface of 'base T0. The magnet yis he1d'inplaceby 'a cross plateZ 5 which extends over the-arms of .the 'magnet and'islheld .inplace by screws v2'5wliich are threadedlyengage'd in basefl'll. Asillustrated hereinthe respective ends, '96 Vand *958, :of the 'voice coil winding 28 y.are 4led through base ,plate 'lllintothe space T00 situated below 1theyoice c'o'il "and dned 'by the downwardlyprdjecting base gpl'atefflanges |112. and I M,

55 and the removable vcoverpla'te 1136, which is disengageably secured to the said flanges as by means of screws |08. The said ends 96 and 98 are attached to a socket llll which is adapted to receive the contacts of a plug connector (not shown) leading to a source of electric impulses, such for example as a microphone.

Preferably stops or positioning lugs 38 are provided extending upwardly from the base member I to aid in preventing unseating of magnet 24 in the event of shock to the device, such as might result if the device should be accidentally dropped or struck.

The armature 26 is attached at one end, as' by screws 40, to an arm 42 the bifurcated end of which is pivotally mounted within the chamber on shaft 44, which is supported between the lugs 46 extending upwardly from base member I0.

On the under side of arm 42, adjacent its connection to said armature 26, a valve seat is provided adapted to receive a grid valve or diaphragm 48, which, as illustrated herein, is a disc-like member having a solid marginal portion 50 enclosing a central area comprising the alternate parallel slots 52 and intermediate web portions 54 reinforced by the circular unslotted portion or rib 56. Diaphragm 48 is supported by arm 42 so that its upper surface is spaced from the body of the arm permitting ready access of air within the chamber to the upper surface of said diaphragm,

The inner end of air outlet passage 60 is provided with a valve seat to receive a diaphragm 62, which may correspond exactly to member 48, the seats for members 48 and 62 being generally aligned but slightly offset horizontally so that the movable diaphragm member 48 may be superimposed upon fixed diaphragm 62, with the unslotted portions thereof including the marginal portion overlying and respectively covering all the slots or open portions of diaphragm 62 whereby an air seal will be provided when the surfaces of the said diaphragms are in contact.

It will thus be seen that the two diaphragm members 48 and 62 cooperate to form air valve means, and that although a stream of air passes freely through either diaphragm 48 or diaphragm 62 when said members are separated, said members coact to provide an air seal when movable member 48 is superimposed upon xed member 62.

It will thus be seen that when armature v26 is vibrated, as by the alternate attractive and repulsive force of voice currents flowing through voice coil 28 and amplified by the permanent magnet 24, the vibratory movements of the armature 26 will be communicated to pivoted arm 42 and to diaphragm 48 causing diaphragm 48 to set up air impulses within said chamber and thereby modulating a stream of air flowing through said chamber. Such a stream of air may be introduced into the chamber, from any suitable source, such as a supply of compressed air, through the inlet passages 58, which are shown herein provided at spaced intervals around an air outlet passage or embouchure 60, which may be of a known kind desirably serving to amplify the sound impulses created within the chamber, and discharging into the chamber under arm 42.

Arm 42, which, it will be noted, extends substantially at right angles to air outlet passage 60, is rotated around a pivot which is spaced a considerable distance from valve member 48, and thus, in moving with armature 26 through the very narrow range of vibratory movement (a few thousandths of an inch) of armature 26 the arm will maintain diaphragm or valve member 48 in a plane which is substantially parallel to the plane of valve member 62. Accordingly when the valve member 48 moves away from contact with valve member 62 all of the slots of both members will immediately be uncovered and open for the passage of air, thus permitting a maximum of air flow through the valve members, thereby facilitating maximum sound amplication.

The air inlets 58 deliver air into the chamber under said arm 42. During the operation of the device the bottom surface of valve member 48 and the surrounding portion of arm 42 is spaced from the upper surface of fixed valve member 62, which is substantially in the plane of the discharge ends of the air inlets, by a, distance on the order of .003 of an inch. The incoming air impingesv directly upon the portion of arm 42 surrounding the valve seat for diaphragm 48, and thus resists closing of the valve members and tends to revolve arm 42 in a clockwise direction around its pivot shaft 44. The resistance the incoming air streams exert against the closing movement of valve member 48 increases progressively as the valve closes, thus cushioning the closing of the valve members and preventing them from striking together with force sufficient to set up undesirable interfering vibrations.

The incoming air thus tends to float the arm 42yand this floating effect of arm 42 is further promoted by means of lever arm 64 which has a portion 63 adapted to extend between the bifurcated ends of arm 42, and is pivotally mounted on shaft 44 on which member 42 is also'mounted as has been explained. Portion 63 of lever arm 64 has a cross-bore 65 through which the shaft 44 extends the ends of the shaft also extending through bores in the bifurcated ends of arm 42 and being retained by screws 'l0 extending through lugs 46 respectively into recesses 12 in the ends respectively of shaft 44. The end of lever 64 which is on the opposite side of pivot shaft 44 from the diaphragm 43 is adjustably connected by link 66 to a pressure responsive member 68, which may comprise a collapsible means, such for example as a bellows of well known construction, mountedwithin the chamber, and in effect forming a wall portion thereof. The pressure responsive member 68 tends to expand outwardly, and thus to increase the space Within the chamber, when air is admitted to the chamber, thus pulling link 66 downwardly and causing lever 64 to be rotated in a clockwise direction.

In order to provide for accurately adjusting the position of diaphragm 48 with relation to diaphragm 62, and to align the closed portions of one diaphragm with the open portions of the other diaphragm so that in superimposed position they will form an effective air seal, the arm 42 and the lever 64 are provided as separate members mounted on a common pivot shaft 44. Means are provided for interengaging arm 42 and lever 64 so that in effect they form together a unitary pivoted arm having pressure responsive means at one end, and the diaphragm 48 and the armature 26 adjacent the other end, the means illustrated comprising a pair of adjusting screws I4 extending through the internally threaded bores 'l5 extending horizontally through the spaced arms of member 42, respectively, said pressure screws 14 having pointed heads adapted to be received in conical recesses 'I6 provided in the lateral edges respectively of the portion 68 of lever 64 projecting forwardly of itspivotal mounting on shaft 44. By means, of the adjustment screws 'I4 the member 42 and part 6 3 may be secured together for rotation in unison around the center pivot shaft 44 and the. position of member 42 may be adjusted laterally thus further facilitating the accurate positioning of diaphragm or valve members 48 and 62 relative ,to one another.

In order to increase the balanced, oating character of arm 42 means are provided for limiting the amplitude of vibration of arm 42. As illustrated herein this means comprises the springs 'I8 and 80, mounted on and around a rod 82, which extends through the vertically aligned bores S6 and 84 in arm 42 and in base member I0 respectively, and is threaded at its end to receive a nut 82a serving to hold the rod in place and to adjust the tension of springs 18 and 80. Spring 78 is retained between the head Y88 of rod 82, and the upper surface of arm 42 at 90. Similarly spring 8D is retained between the under surface of arm 42 and the top surface of portion 92 projecting upwardly from base member I0. Springs 78 and 80 thus serve to damp out vibrations of arm 42 which are greater than a predetermined amplitude and thus serve to limit the clockwise motion of arm 42 produced by the action of an inflowing air stream and the pressure responsive member 68.

It will be noted that the pivoted lever arm means which supports the movable valve or diaphragm member 48 extends substantially at right angles to both the air inlet and outlet passages and that because of this mounting and the"float ing effect achieved through the combined effect and coaction of the incoming air upon the under surface of arm 42 and the reaction thereto of pressure member 68, a delicate balancing of armature 28 is achieved rendering it highly responsive to actuation by the vibration inducing means.

Because of the improved balancing of arm 42 not only the armature 26 is rendered very susceptible to vibration creating impulses but the same is true with regard to movable valve or diaphragm 48 which is thus caused to set up sound waves modulating an air stream owing through the chamber. And because the upper valve member 48 in moving toward and away from the lower valve member 62, maintains a substantially parallel relationship to said lvalve member 62 at all times due to its distance from pivot shaft 44, the slots throughout the entire area of both valve members are effectively open for the passage of air, except when the valve members are momentarily in superimposed contact with one another, when the flow of air through the outlet 60 will be entirely cut off.

It will thus be seen that there has been provided by this invention a method and apparatus in which the various objects hereinabove set forth together with many thoroughly practical advantages are successfully achieved. As various possible embodiments might be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, al1 without departing from the scope of the invention, it is to be understood that al1 matter hereinbefore set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

What I claim is:

1. In a sound reproducing and amplifying unit of the type having a movable valve member for modulating an air stream in accordance with movement of a vibrating armature, a chamber closed except for air inletl and outlet passages, a rst valve member extending across said outlet passage, an arm assembly pivotally supported within said chamber on a pivot located intermediatethe ends of said assembly, a second valve member mounted on said assembly adjacent its end which is remote from said pivot and movable with said assembly into and away from a position of superimposition upon said rst valve member, said valve members when separated each being adapted to pass an air stream but cooperating to form an air seal when superimposed,V and means connected to said arm on the other side of the said pivot from said second valve member and adapted to regulate the angular position of said arm on its pivot, and to separate said valve members, when an air stream is passed through said chamber, thereby conditioning said arm to respond to vibrations of an armature connected to said arm.

2. In a device for translating electrical impulses into sound and amplifying them, a hollow chamber, closed except for having inlet means adapted for connection to a source of air under pressure, and an outlet, a first valve member xed in position across said outlet, an arm pivotally disposed within said chamber on pivot means adjacent one end of said arm, and a second valve member mounted on said arm adjacent its other end for swinging movement therewith toward and away from said first valve member, said valve members being individually air permeable but adapted to form an air seal when brought together, an armature carried by said arm, and a voice coil positioned relatively to said armature to cause said armature to be vibrated by voice currents transmitted through said coil, pressure responsive means, and a pivoted lever associated with said.

pressure responsive means and with said pivoted arm whereby when compressed air is admitted toA said chamber said lever is pivoted thereby pivoting said arm to move said second valve member away from said rst valve member thereby opening said outlet and permitting a stream of air under pressure to flow through said chamber and rendering said second valve member responsive to vibrations of said armature induced by voice currents within said voice coil, to modulate said stream of air.

3. A device according to claim 2 in which there is provided means for adjusting said arm laterally to control the relative position of said first and second valve members.

4. A device according to claim 2 in which said arm and ysaid lever are pivotally mounted on a common shaft, and there is provided means for interengaging said arm and said lever for movement in unison around said shaft.

5. A device according to claim 2 in which said arm and said lever are pivotally mounted on a common shaft, and there is provided means for interengaging said arm and said lever for movement in unison around `said shaft, means for adjusting said arm and lever laterally, and means for adjusting the position of said arm angularly with respect to said lever to control the relative position of said valve members.

6. A device according to claim 2 in which the said air inlet is arranged to discharge into 4said chamber directly against the under side of the portion of said arm which is adjacent to said armature.

'7.I In a loud speaker adapted to reproduce and amplify sound, a chamber having an arm pivotally mounted therein, a grid valve carried by said arm on one side of its said pivot, means connected to said arm on the other side of said pivot for balancing said arm when a stream of air is passing through said chamber, said chamber having an air outlet passage the inner end of which is aligned with said diaphragm, a plurality of air inlet passages disposed around said air outlet passage and adapted to deliver air into said chamber around the periphery of said grid valve into contact with said arm thereby cooperating with said balancing means for balancing said arm and swinging said grid valve with said arm away from the mouth of said air outlet passage when a stream of air is passing through said chamber, and thus together with said balancing means rendering said pivoted arm extremely sensitive to vibrations, and means for vibrating said arm thereby simultaneously vibrating said grid valve and causing modulation of an air stream passing through said chamber.

8. In a loud speaker adapted to reproduce and amplify sound, a'chamber having an arm pivotally mounted therein, a grid valve carried by said arm on one side of its said pivot, means connected to said arm on the other side of said pivot for balancing said arm when a stream of air is passing through said chamber, said chamber having an air outlet passage the inner end of which is aligned with said grid valve, an air inlet passage surrounding said air outlet, and means for vibrating said arm including an armature projecting from said arm at a point remote from said pivot thereby simultaneously vibrating said grid valve and causing modulation of an air 'stream passing through said chamber.

9. In a device for translating electrical impulses into sound and amplifying them, a charnber, an air inlet passage communicating with said chamber, an air discharge passage leading from said chamber, a stationary grid valve positioned across said discharge passage, an arm pivotally mounted in said chamber, a grid valve supported by saidarm and movable with the arm from a closed position in which it is superimposed upon said stationary grid valve to a position in which it is separated from said stationary grid permitting air to be discharged through said stationary grid valve, said air inlet passage opening into said chamber directly beneath said pivoted arm whereby the incoming air tends to rotate said arm in-a direction to separate the grid which is carried by said arm from said stationary grid.

10. A device aslclaimed in claim 9 in which the air inlet passage discharges under said pivoted arm at a point remote from said pivot.

11. A device as claimed in claim 9 in which said arm -comprises two parts, means for interconnecting said parts for movement in unison and for adjusting the position of one of said parts laterally in relation to the other of said parts.

12. A device as claimed in claim 9 in which the said air inlet is disposed in the wall dening the said air discharge passage.

13. A device as -claimed in claim 9 in which said arm has an armature mounted thereon and extending from it at a point removed from the pivot of said arm.

JOSEPH L. FODOR.

REFERENCES CITED The following references are of record in the le of this patent:

`UNITED STATES PATENTS Diiks sept. 4, 1945 

